The 2014 Chevrolet Malibu gets a new base engine, and with it come new, higher fuel-efficiency ratings from the EPA.

But does the improved gas mileage mean the Malibu Eco model no longer has a reason to exist?

For the new model year, Chevy made a large number of changes to the year-old vehicle, which has not sold as well as GM had hoped.

2014 Chevrolet Malibu

2014 Chevrolet Malibu

Critics had slammed its reduced rear-seat room, among other issues, in the hotly competitive mid-size sedan market. 

Among the changes for 2014 were modifications to the base 2.5-liter engine that boosted the EPA combined rating from 26 mpg for 2013 to 29 mpg for the new model year.

As Automotive News points out, that's the same combined rating as the Malibu Eco, whose powertrain carries over unchanged into the revised 2014 model--and which costs $2,700 more than the base-model 2014 Malibu with the engine updates.

Launch pulled forward

You may recall that the all-new 2013 Malibu, launched early in 2012, was sold only as an Eco model for several months.

The new 2.5-liter base engine simply wasn't ready at the launch date--which had been pulled ahead several months by CEO Dan Akerson.

For 2014, that engine has already been updated; among other changes, Chevrolet added as standard a start-stop feature that switches off the engine when the car comes to rest.

2014 Chevrolet Malibu

2014 Chevrolet Malibu

The result is that the base 2014 Malibu now equals every EPA rating of the Malibu Eco: not only 29 mpg combined, but 25 mpg city and 36 mpg highway too.

And this has happened before.

An earlier generation of GM mild hybrids, then known as Belt-Alternator System, was offered on the previous-generation Chevy Malibu in 2008 and 2009, rated at 27 mpg combined.

But when GM upgraded the transmission from an old four-speed automatic to its new six-speed automatic, the combined rating for the Malibu with the base 2.4-liter engine rose from 25 mpg to 26 mpg--a 1-mpg difference, for a price more than $2,000 lower.

Has history just repeated itself?

Eco or eAssist: mild hybrid

The Malibu Eco model uses an older 2.4-liter four-cylinder engine that uses a belt-driven starter-alternator unit. It can start the engine, add electric torque to the engine using energy stored in a small lithium-ion battery pack in the trunk, and recharge that battery under regenerative braking.

The system, known as eAssist, is also fitted to the Buick Regal and Buick Lacrosse--but it hasn't been hugely popular on any of the three GM models that feature it.

2012 Buick Regal with eAssist

2012 Buick Regal with eAssist

Buick made the eAssist engine the base Regal offering for 2013--it was optional in 2012--but only about 20 percent of Regal buyers stuck with the 29-mpg mild-hybrid powertrain, with most upgrading to the less-efficient 2.4-liter four or the more powerful 2.0-liter turbo four (both rated at 23 mpg last year).

So for 2014, Buick has moved to a third base engine in three years for the Regal: It's the 259-horsepower turbocharged 2.0-liter four, now rated at 24 mpg combined against the 29 mpg of the Regal eAssist.

Mild sales too

Through the first eight months of the year, General Motors has sold 18,942 Buick and Chevrolet cars with the eAssist mild-hybrid system, the bulk of them Malibu Ecos.

That total represents 10 percent of the 186,823 total for those three models. Broken down, the system is chosen in 8.1 percent of Malibus, 15.1 percent of Lacrosses, and 19.6 percent of Regals.

And it begs the question: With GM having said several years ago it expected to sell 100,000 or more mild hybrids a year, is the system proving less popular than planned?

2014 Chevrolet Malibu

2014 Chevrolet Malibu

The company said last year it would downplay full hybrids and focus both on the eAssist mild-hybrid system and its Voltec range-extended electric powertrain.

But can the mild-hybrid system continue to deliver fuel-efficiency gains significant enough to justify its price and complexity?

Automotive News quotes Pam Fletcher, GM's executive chief engineer for electrified vehicles, as saying only that the company would continue to improve the eAssist system--and that GM felt it was a leader in the technology.

Buick eAssist Hybrid Technology

Buick eAssist Hybrid Technology

That's effectively a wait-and-see response.

We might expect an eAssist version of the new, more modern 2.5-liter four to replace the current powertrain using the mild hybrid with the older 2.4-liter engine, for instance.

All-electric running needed?

But Honda, the only other company to produce large numbers of mild hybrids, has released plans to move toward a stronger hybrid system for small cars that will offer some amount of all-electric running.

Honda has built mild hybrids since 1999, but recently introduced a full hybrid system for its 2014 Honda Accord Plug-In Hybrid as well as the upcoming Acccord Hybrid model.

If you're going to electrify a car--even if you don't call it a "hybrid"--do consumers increasingly expect it to be able to run on electricity alone?

As Jalopnik puts it, do you need to "go big or go home"?

Or is the lumpy driving and engine response of eAssist fitted to some GM cars, and its narrowing fuel-efficiency gains, more the problem here?

Leave us your thoughts in the Comments below.


Follow GreenCarReports on Facebook, Twitter, and Google+.